Idas was the son of Aphareus and Arene in Greek mythology, and brother of Lynceus. The two brothers were suitors of Hilaeira and Phoebe, who were also courted by the twin brothers Castor and Pollux. The feud ended with the death of Castor. Idas also participated in the Argonautic Expedition helping Jason to find the Golden Fleece, while he also took part in the hunt for the Calydonian Boar.

Idas later tried to seduce Marpessa, who was also wanted by the god Apollo. Zeus told Marpessa to choose between the two suitors, and she picked Idas, fearing that Apollo would later abandon her. Idas and Marpessa had a daughter, Cleopatra.